We report here the observation of the phonon sidebands of a bound exciton by resonant excitation of the bound exciton. By exciting fluorescence in impure samples of GaP with different laser lines one can obtain spectra in which lines associated with particular impurities show enhancement. Thus resonant fluorescence can be used as a spectroscopic tool for the study of exciton spectra in solids. We suggest this method as a possible technique for identifying unknown lines with specific impurities and as an application for tunable dye lasers.